This application is based on Patent Application No. 2001-232922 filed Jul. 31, 2001 in Japan, the content of which is incorporated hereinto by reference.
1. Field of the Invention
The invention relates to inkjet printing apparatuses and methods for detecting the amount of remaining ink in the inkjet printing apparatuses, and particularly, to a method for detecting remaining ink level.
2. Description of the Related Art
Some of the conventional printing apparatuses such as inkjet printers, which use ink for printing, execute detecting of the remaining ink level so as to stop a printing operation or to provide an indication urging users to exchange the ink tank, when ink has run out or the ink level has become as low as to cause problems in printing. As methods for detecting ink levels, there have been proposed a variety of methods. For example, sensors are known as those directly detect the presence/absence of ink or a remaining level of ink, such as optical sensors utilizing a light interception by ink, electric sensors utilizing electric resistance change due to the presence/absence of ink, and mechanical sensors utilizing a lever that moves together with the ups and downs of the ink level. There is also a method that accumulates data about ink consumption during operations such as printing and recovering and then estimates the remaining level based on the accumulated data.
In detecting the amount of remaining ink, especially in the method of estimating the amount of remaining ink by calculation, it is necessary to know that the ink tank is in a initial state after detecting the ink tank replaced with new one, that is, is in a state filled with ink. For this purpose, there has been proposed various methods for detecting replacement of the ink tank. For example, a method that directly detects mounting and detaching of the ink tank by using a sensor, a method that indirectly knows the change of ink tank by regarding a change from a state of absence of ink in the tank into a state of presence of ink as the change of the ink tank, and a method that supposes the change of the ink tank by detecting that an operation relevant to the replacement of the tank is done by a user, are known.
It is possible to check if the remaining ink level has fallen below a predetermined level by the use of the optical, electric and mechanical sensors of relatively simple structure and low cost. These sensors, however, have such disadvantages that the control process becomes complex and additional cost arises from detection components when estimating the remaining ink level in detailed scales.
On the other hand, the method for estimating the remaining ink level based on the accumulated data of ink consumption has the advantage of being capable of estimating the remaining ink level in detailed scales at relatively low cost. However, there are variations in the estimate of ink consumption due to variations in the ejection quantity and performance of the recovering mechanism. In addition, the capacity of the ink tank and the amount of filled ink may also vary. As a result, the estimated remaining ink level may significantly differ from the actual ink level. Further, it is also necessary to introduce some margin in the estimate of ink levels, taking such errors into account. Then, in turn, such a problem arises that the printing is stopped or the indication of ink-out is issued although the ink tank still has ink.
Further, in the method of detecting the replacement or change of the ink tank, it may occur that even when the ink tank is detected to be the state of absence of ink, ink flows in an inverse direction from a path between the ink tank and a printing head to the ink tank, depending on an operation condition of an apparatus or an environment condition, and then detecting the state of absence of ink may be changed to detecting the state of presence of ink in spite of not doing the change of the ink tank. For this reason, if the replacement of the tank is judged to be done in accordance with the change from the state of ink absence to the state ink presence and the amount of ink in the ink tank is set to be full in the remaining amount detecting processing, there may occur a certain difference between the detected amount of ink and an actual amount of ink.
Also, in the method of knowing the change of the ink tank by detecting the operation relevant to the change of the tank done by the user, if the same tank as that has been used is again mounted and this mounting operation is detected as the change of the ink tank, there may occur a certain difference between the detected amount of ink and an actual amount of ink similarly to the above method. This problem may occur also in the method of directly detecting the replacement of the tank by using the sensor.
The object of the present invention is to provide an inkjet printing apparatus and a remaining ink level detection method that detect a change of an ink tank precisely and based on the detection of the change detect the remaining ink level precisely in detailed scales with a low-cost and simple structure using a sensor.
In the first aspect of the present invention, there is provided a remaining amount detecting method of detecting an amount of remaining ink in an ink reservoir, comprising the steps of:
providing sensing means for detecting whether the amount of remaining ink in the reservoir is below a predetermined level or not, ink presence/absence memory means for storing as to whether the sensing means detects that the amount of remaining ink is below the predetermined level or not, and replacement memory means for storing as to whether the ink reservoir is changed or not;
when the sensing means detects that the amount is not below the predetermined level, the ink presence/absence memory means stores that the sensing means detects that the amount of remaining ink is below the predetermined level, and the replacement memory means stores that the ink reservoir is changed, determining the amount of remaining ink as a amount that fills the ink reservoir; and
when the sensing means detects that the amount is not below the predetermined level, the ink presence/absence memory means stores that the sensing means detects that the amount of remaining ink is below the predetermined level, and the replacement memory means stores that the ink reservoir is not changed, determining the amount of remaining ink as a amount that is obtained by correction increasing the amount of remaining ink to be greater than the predetermined level.
In the second aspect of the present invention, there is provided an inkjet printing apparatus using a printing head for ejecting ink and an ink reservoir for storing ink supplied to the printing head to perform printing on a printing medium, and detecting an amount of remaining ink in the ink reservoir, the apparatus comprising:
sensing means for detecting whether the amount of remaining ink in the reservoir is below a predetermined level or not;
ink presence/absence memory means for storing as to whether the sensing means detects that the amount of remaining ink is below the predetermined level or not;
replacement memory means for storing as to whether the ink reservoir is changed or not; and
remaining ink amount determining means for, when the sensing means detects that the amount is not below the predetermined level, the ink presence/absence memory means stores that the sensing means detects that the amount of remaining ink is below the predetermined level, and the replacement memory means stores that the ink reservoir is changed, determining the amount of remaining ink as a amount that fills the ink reservoir; and
when the sensing means detects that the amount is not below the predetermined level, the ink presence/absence memory means stores that the sensing means detects that the amount of remaining ink is below the predetermined level, and the replacement memory means stores that the ink reservoir is not changed, determining the amount of remaining ink as a amount that is obtained by correction increasing the amount of remaining ink to be greater than the predetermined level.
According to the above configuration, in determining a remaining amount of ink, when the sensing means does not detect that the remaining amount is equal to or less than a predetermined level, the ink presence/absence memory means stores that the sensing means detects that the remaining amount is equal to or less than the predetermined level, and the change memory means stores that the ink reservoir has been changed, the remaining amount is determined as that is full in the ink reservoir, and when the sensing means does not detect that the remaining amount is equal to or less than the predetermined level, the ink presence/absence memory means stores that the sensing means detects that the remaining amount is equal to or less than the predetermined level, and the change memory means stores that the ink reservoir has not been changed, the remaining amount is determined as that is obtained by correcting the amount to be increased to that greater than the predetermined level. Thereby, it can be estimated either the remaining amount in the ink tank actually becomes greater than the predetermined level by mounting new ink tank or the remaining amount becomes greater than the predetermined level owing to for example occurrence of an inverse ink flow from an ink supply path to the ink reservoir, and it is possible to determine the amount of remaining ink correspondingly to that estimation based on the result of the estimation.
The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.